It is known to provide structures into which concrete or other filler material may be poured for forming a vertical wall, such as swimming pool walls. It is often desired to customize the arcuate configuration of such walls however, the size, shape and curvature of known concrete wall forming structures are commonly predetermined or are not easily adjustable. For example, U.S. Pat. No. 5,535,565 discloses a plurality of panels having a pair of opposed front and back face plates being interconnected at their ends by webs extending across the span between the face plates. The panel structures are not flexible. The curvature of the structure is predetermined by varying the length of connectors which are secured across front plates and back plates of adjacent panels.
U.S. Pat. No. 6,012,699 and U.S. Pat. No. 4,679,763 each discloses a metal form having a flexible panel member with a plurality of perimetral, spaced apart flanges projecting from one side thereof and having a face for forming concrete on the other side. The panel is flexed in a predetermined curvature and secured therein by a securing straps across adjacent flanges. To form a concrete wall structure, a pair of matching shaped wall structures must be arranged and stabilized a suitable distance apart for pouring concrete therebetween.
U.S. Pat. No. 4,915,345 discloses a concrete forming structure which may be preassembled into various arcuate curvatures. U.S. Pat. No. 5,729,944 discloses a concrete forming structure capable of accepting concrete therein, but its curvature is not adjustable.